An Alternate Approach to Friction Factor Computations Based on Entropy Generation in Gas Micro Flows

The gas micro flows are deployed in heat-sinks of many practical micro devices, and cooling systems for gas turbine blades etc. In present study, fluid friction characteristics of laminar micro flow, operating at low Reynolds number, are studied. This flow model is representative of fluid flows in many micro device applications. Fanning friction factor computations were re-modeled using ‘entropy generation’ and ‘axial temperature rise’ in the flow domain. Entropy generation considerations and adiabatic wall boundary condition isolate viscous dissipation effects from other causes of heating. Navier-Stoke and energy equations were numerically solved for constant properties gas (air) flow in circular micro pipe using ANSYS/FLUENT® software and post processing in C++. The results of present study show good agreement with the well established classical Hagen-Poiseuille correlations, experimentally validated methods of Morini, and Celata et al. Present method is useful where the laboratory facilities for micro flow experiments are not available.